It is known practice to dye keratin fibers, such as human hair, with dye compositions comprising oxidation dye precursors, such as ortho- or para-phenylenediamines, ortho- or para-aminophenols, and heterocyclic compounds, which are generally referred to as oxidation bases. These oxidation bases can be colorless or weakly colored compounds which, when combined with oxidizing products, may give rise to colored compounds by a process of oxidative condensation. It is also known that the shades obtained with these oxidation bases may be varied by combining them with couplers or coloration modifiers, wherein the coloration modifiers can be chosen from, for example, meta-diaminobenzenes, meta-aminophenols, meta-diphenols and certain heterocyclic compounds such as indole compounds. The variety of molecules used as oxidation bases and couplers makes it possible to obtain a wide range of colors.
The “permanent” coloration that can be obtained by these oxidation dyes, moreover, may satisfy at least one of a number of requirements. For example, it may not have toxicological drawbacks, it may be able to allow shades of the desired intensity to be obtained, and may be able to have good resistance to external agents such as light, bad weather, washing, permanent waving, perspiration and rubbing. The dyes may also be able to allow white hairs to be covered and, lastly, they may be as unselective as possible, that is to say that they may be able to allow the smallest possible differences in coloration to be produced over the entire length of the same keratin fiber, which is generally differently sensitized (that is to say damaged) between its end and its root.